Method of and apparatus for filtering

ABSTRACT

A method of filtering utilizes a filtering apparatus having a filter member presenting a plurality of flow paths therethrough of a form to retain at least a portion of the material to be extracted the method comprising the steps of passing a stream of fluid to be filtered in a forward direction from an inlet through the filter member, moving the filter member out of the stream of fluid, changing the geometry of the filter member under gravity, e.g. by inverting the filter member, to assist in removal of extracted material from the filter member.

This invention relates to a method of and apparatus for filteringmaterial from a fluid stream containing such material.

The material filtered from the fluid stream which may be a gaseous fluidor a liquid fluid usually comprises solid state particles. The materialextracted, however, may include material of quasi solid form such as gelparticles or globule particles of a fluid, more viscous than that whichforms the main stream of fluid to be filtered and which may either beintrinsically able to coalecc into such globule particles or adhere tosolid state particles. The term "extracted material" as used hereinincludes both solid state and quasi solid material. The maximumcross-sectional size of passageways afforded by a primary filter memberincorporated in the filtering apparatus is determined by the averagesize of the particle which it is desired to filter from the fluidstream.

One of the problems encountered in methods of an apparatus for filteringis that the passageways afforded by the filter member become blocked orclogged by extracted material. This is especially the case if the fluidto be filtered contains particles having a wide spectrum of sizesbecause the passageways in the filter member may quickly become blockedinitially by larger sized particles. If this clogging occurs, the filtermember may thus filter from the fluid stream, particles of smaller sizethan the passageways in the filter member.

Eventually the clogging results in the severe reduction of the rate offlow of the fluid to be filtered through the primary filter member, andpossibly preventing such flow altogether.

Further, filtering apparatus are known which have a secondary filter,finer than the primary filter, to filter fine particles which passthrough the primary filter member, from the fluid stream. Such secondaryfilters also become clogged, in use.

Thus it is often the case that filter members require to be subjected toaction to remove extracted material therefrom.

The object of the present invention is to provide a method and a form offilter member which facilitates this operation.

According to one aspect of the invention, we provide a method offiltering utilising a filtering apparatus having at least one filtermember presenting a plurality of flow paths therethrough of a form toretain, in use, at least a portion of material to be extracted (hereincalled the extracted material) from a stream of fluid to be filtered,characterised in that said method comprises the steps of passing astream of fluid to be filtered through the filter member with the filtermember in a filtering position, moving the filter member out of thefluid stream, changing the orientation of the filter member undergravity, to remove extracted material from the filter member.

Because the change in orientation of the filter member is achieved undergravity, there is no necessity to provide any method step or means, foracting on the filter member to cause said change in orientation althoughas described below the filter member may be flushed if required.

It will be appreciated that as the orientation of the filter member ischanged, extracted material collected by the primary filter member isremoved from the filter member, as the geometry of the filter memberwill change.

From a second aspect, the invention resides in the provision of afiltering apparatus for filtering material from a stream of fluid to befiltered, said apparatus comprising at least one filter member which,when in a filtering position, presents a plurality of flow pathstherethrough to the stream of fluid, means to move the member out of thestream of fluid, means to change the orientation of the filter memberunder gravity from the filtering position in which the member presentsconstriction to said fluid in a forward direction so that material isextracted from the fluid by the filter member, to another positionwherein extracted material is removed from the filter member.

The filtering apparatus may have a plurality of filter members provided,each comprising a section of a continuous belt conveyor, and eachpresenting said flow paths to the stream of fluid, the belt beingmovable to move each filter member in turn from its filtering positionin which the fluid is constrained to pass in the forward directionthrough the flow paths, to said another position out of the fluid flow,at which the orientation of the filter member may be changed.

The invention will now be described, by way of example, with referenceto the accompanying drawing in which:

FIG. 1 is a side schematic sectional view of filtering apparatus inaccordance with the second aspect of the invention for use in the methodaccording to the first aspect of the invention;

FIG. 2 is a perspective view, partly broken away, of a practical form ofthe embodiment shown in FIG. 1.

Referring first to FIG. 1, a filtering apparatus 200 comprises aplurality of filter members, some of which are indicated at 211a, 211b,211c each comprising a section of a continuous belt conveyor. The belt211 is received around a pair of sprockets 212, 213 rotated aboutrespective axes 214,215 by any desired drive means.

An upper length of belt 211 which extends between the sprockets 212, 213is located beneath a duct 216 of a coolant fluid system, so that coolantfluid contaminated with swarf and the like will pass from the duct 216through the belt by which the swarf and other material is extracted, toenable the coolant to be re-cycled.

The filter members 211a, 211b, 211c, each have a base member 225comprising a pair of strips, one strip either side of the belt betweenwhich extend in each filter member 211a, 211b and 211c a retainingelement comprising a wire 226.

The strips which form the base member 225 are each interconnected toallow movement between the sections as hereinafter described, and eachhave means to engage the sprockets 212, 213 so that drive is transmittedto the belt 211.

For example, the sprockets 212, 213 could be toothed, in which case thestrips or one of the strips could comprise a chain to receive the teethof the sprockets 212, 213 or alternatively, the drive may be transmittedby friction only or in any other desired manner.

The sections 211a, 211b, 211c each have side members 227 which extendaway from the base member 225 either side of the belt.

Although the base members 225 for each of the filter members areinterconnected, the side members 227 are disjointed so that as thefilter members engage around the sprockets 212, 213, the sections canseparate and thus move relative to one another, although when thesections are beneath the duct 216, i.e. in a straight run between thesprockets 212,213, the side members 227 engage one another and form acontinuous filter bed.

The retaining elements 226 each retain a filter element 220. It can beseen that along the straight run at the upper side of the belt 211adjacent the duct 216, the filter elements 228 overlap. In the presentcase, the sprockets 212, 213 rotate clockwise and the filter elements228 overlap so that each filter element 228 overlaps the next leftfilter element.

The filter elements 228 are not constrained at their sides remote fromthe retaining elements 226 and are thus free to pivot either about thewires or are attached to the wires 226 which are themselves free topivot relative to the base members 225.

The filter elements 228 are each made of aluminum or other metal gauze,or material which may be impregnated so as not to be absorbent of thecoolant to be filtered.

The filter elements 228 thus present a plurality of flow paths throughthe filter members 211a, 211b, 211c to remove extracted material fromthe fluid to be filtered as the sections of the belt 211 pass into thefluid flow beneath duct 216.

The sprockets 212, 213 may be rotated in steps as required, butpreferably are continuously rotated slowly so that fresh parts of thebelt 211 are continuously located beneath the duct 216 and thuspresented to the stream of fluid to be filtered.

As the filter member sections of the belt 211 move away from beneath theduct 216, they carry with them extracted material, whilst the filteredfluid passes through the belt 211 for further filtering as hereinafterdescribed. Because the filter elements 228 are free to pivot, they willbegin to separate from one another from the overlapped position as thefilter members 211a, 211b, 211c engage the sprocket 213, under theinfluence of gravity. As the filter members reach the position at whichfilter member 218 is shown, the filter elements 228 will be generallyvertical and the extracted material on the filter elements 228 willbecome dislodged and thus removed under gravity downwardly from the belt211. Of course, by the time the filter members disengage the sprocket213 to travel along the lower straight section, e.g. at the positionoccupied by filter member 217, the filter elements 218 will be invertedhanging vertically retained by their retaining elements 226.

If desired, means may be provided such as a reverse flow of fluidthrough the filter elements 228 to flush the filter elements 228 withfluid as they pass along the lower straight 219 of the belt 211.

As the filter members 211a, 211b, 211c engage sprocket 212, the filterelements 228 will again assume their overlapped position, again undergravity and when they disengage the sprocket 212, they will againpresent in their overlapped extracted material free condition, flowpaths therethrough for the fluid to be filtered introduced through theduct 216.

Thus the filter elements 228 will be continuously cleaned allowing forcontinuous filtering of the fluid without any need to periodically stopfiltering and remove extracted material from the filter members.

After prolonged use, it may be required to present the opposite sides ofthe filter elements 228 to the fluid to be filtered so that the fluid tobe filtered will flush and remove any stubborn extracted materialattached to the previously upward facing surface. This can be simplyachieved in this embodiment by reversing the direction of rotation ofthe sprockets 212, 213. The filter elements 228 will assume an oppositeoverlapped condition, i.e. each filter element 228 will overlap the nextright filter element.

It can be seen that located inwardly of the belt 211, a second conveyorbelt 230 is provided which is carried by a further pair of sprockets231, 232 which also rotate about axes 214, 215, the belt 230 alsocomprising a plurality of filter member sections similar to the belt211.

Preferably, the sprockets 231 and 232 rotate in the same direction asthe sprockets 212 and 213 and thus may be driven from a common drivemeans.

The construction of the belt 230 is substantially similar to theconstruction of the belt 211, although the filter elements of the filtermembers are smaller, but could be of the same or larger size as theelements 218 of belt 211.

Furthermore, the fluid flow paths presented by the filter elementsthereof are smaller so that the second filter members provide a finerdegree of filtering than the first filter members 211a, 211b, 211c.

The fluid which passes from duct 216 through the first filter members ofbelt 211 is guided by a guide 240 to pass through the second filtermembers of belt 230. The thus twice filtered fluid is then removed froma space 241 inwardly of the second belt 230 by suitable duct means (notshown) for recycling.

Alternatively, the belt conveyor could be arranged to permit thefiltered fluid to pass through the lower tracks between the sprockets231, 232 also, and to be collected and recycled from space 5. This wouldbe of advantage in that the filter elements of the belt 230 would beflushed, but of disadvantage in that the filtering efficiency would belowered. However this may be acceptable in some circumstances.

The filtering apparatus described with reference to FIG. 1 can be madean integral part of a machine tool or a separate unit as required.

The axes 214,1 215 may be separated by any required distance providedthat the belts 211, 230 are made sufficiently long. If desired, thesecond belt 230 may not be provided, or more than two belts, each withfilter members, may be provided.

Referring now to FIG. 2, a practical example of a continuous conveyorbelt filter apparatus such as described in FIG. 1 is illustrated. Partscorresponding to parts of FIG. 1 are given the same reference numerals.

It can be seen that the apparatus comprises first 211 and second 230belts enclosed in a casing C.

The inlet duct 216 for fluid to be filtered comprises a pipe whichextends for example to a machine tool or group of machine tools fromwhere contaminated coolant is fed.

The filter members 211a, 211b, 211c of belt 211 each have side strips227 pivotally fixed at their lower ends by rivets T₁, to base members225, and are pivotally mounted at their upper ends by studs T₂ to filterelements 228.

The base members 225 extend outwardly of the filter elements 211a, 211b,211c and have locating formations F which are engaged by the teeth ofthe sprockets 212, 213 to impart drive to the belt 211.

The filter elements 228 are carried on a frame R for rigidity, andoverlap at least when between sprockets 212, 213 (only sprocket 213 ofwhich can be seen) to present a continuous filter surface to the fluidintroduced through duct 211.

The second belt 230 is similarly constructed, but has an integral chainL which engages further sprockets 231, 232 (not shown) which rotateabout axes coincident with the axes 214, 215 of rotation of sprockets212, 213.

Swarf which is dislodged from the filter elements 211a, 211b, 211c asthey pass around sprocket 213, is dislodged into a chute H which isremovable from the remainder of the casing to permit of disposal of theswarf.

Filtered coolant passes from the casing by a further duct D forrecirculation as required.

It can be seen that the apparatus is provided on a wheeled carriage Wand thus may be moved around a machine shop for example to any requiredposition.

I claim:
 1. A method comprising: filtering using a filtering apparatushaving first and second filter members each presenting a plurality offlow paths therethrough of a form to retain at least a proportion ofextracted material to be extracted from a stream of fluid to befiltered, at least the first filter member comprising a plurality offilter elements which, when in a filtering position, at least partiallyoverlap, by,passing the stream of fluid to be filtered in one directionthrough the first and second filter members; moving the filter elementsout of the path of the fluid stream so as to preclude clogging of thefiltering apparatus; changing the orientations of both the first andsecond filter members sufficient to enable the filter elements of thefirst filter member to move under gravity to at least partially invertedcleaning positions; and removing extracted material from the first andsecond filter elements.
 2. A method according to claim 1 wherein thechanging step includes the step of rotating the filter members undergravity about an axis transverse to the one direction.
 3. A methodaccording to claim 1 wherein the first and second filter members eachcomprise part of a respective continuous belt made up of sections, atleast one of the sections of each belt having at least one filterelement overlapped with a filter element of an adjacent section, themoving step including the step of moving the sections of the belt from afirst position in which the fluid is constrained to pass in the onedirection through the flow paths to a second position out of the path offluid flow in which the filter elements can move to their cleaningpositions where extracted material is removed therefrom.
 4. A methodaccording to claim 1 wherein during the passing step, the filterelements of the first and second elements upon which the stream of fluidimpinges, are presented generally upwardly, and during the removingstep, the extracted material is discharged therefrom generallydownwardly.
 5. A method according to claim 1 wherein said removing stepincludes the step of subjecting each filter member to a reverse flow offluid.
 6. Filtering apparatus comprising:first and second filter membersof a form to retain in use, at least a proportion of extracted materialto be extracted from a stream of fluid to be filtered, at least thefirst filter member comprising a plurality of filter elements which,when in a filtering position, at least partially overlap; means formoving the first and second filter members out of the stream of fluid;and means for changing the orientations of the first and second filterelements to move the filter elements of the first filter member underthe action of gravity from filtering positions wherein the first filtermember including means for presenting a constriction to the flow offluid to be filtered therethrough in a forward direction so thatmaterial is extracted from the fluid by the first filter member, to atleast partially inverted cleaning positions wherein the extractedmaterial is, removed from the first and second filter members sufficientfor preventing clogging of said first and second filter members. 7.Filtering apparatus according to claim 6 wherein the filter members eachcomprise part of a respective continuous belt made up of sections, atleast one of the sections of each belt having at least one filterelement overlapped with a filter element of an adjacent section, thebelts being movable to move parts of the belt from one position in whichthe fluid is constrained to pass in the forward direction through theflow paths to a second position in which the filter elements can move totheir cleaning positions where extracted material is removed therefrom.8. Filtering apparatus according to claim 7 wherein the filter elementsare each supported by a retaining element secured to the respective beltto permit the filter elements to rotate relative to the belt. 9.Filtering apparatus according to claim 6 including means for subjectingat least the first filter member to a flow of flushing fluid in adirection transverse to the flow of fluid to be filtered to facilitateremoval of extracted material from the filter elements of the firstfilter member when the orientations of the first and second filtermembers have been changed.
 10. Filtering apparatus according to claim 6wherein the filter members are in the fluid stream, a face of eachfilter member is presented upwardly and when the orientation thereof hasbeen changed by inverting the members, the extracted material isdischarged downwardly.